Chafings upon one's inner knees and elbows incurred during activities that require one to be upon one's knees and elbows.

Q: Od's blood, PhD, why limpest thou?
A: Anointest my slutburn with the oil you were planningest to sell to help the poor. It shall prove a salve and balm to my soul, verily, or at least to mine knees and elbows.

an inflammation of the skin caused by overexposure to the sun (sunburn) in certain areas of the body that would only be exposed for long enough to get a sunburn if the person doing the exposing were a slut